OT Cybersecurity Best Practices: How to Align Tools Across Legacy and Modern Systems

Summary

One of the most persistent myths in industrial cybersecurity is that protecting IT and OT environments requires entirely different approaches. In reality, the core technologies—firewalls, access controls, security information and event management (SIEM) systems and endpoint protection—are often the same. What’s different is the context: how the tools are used, why they’re used and where they’re deployed.
 
In 2025 and the years ahead, the challenge is no longer about bridging an IT/OT divide—it’s about building layered, adaptable security architectures that apply familiar tools in environment-specific ways, across both legacy infrastructure and modern digital systems.
 
To do this effectively, organizations need more than the right tools. What’s required is alignment around a shared mission, a clear understanding of operational context and a flexible framework that evolves with the threat landscape.
 
The path forward requires practical, consequence-driven strategies that can adapt to rapidly evolving threats and infrastructure. The following best practices reflect how leading organizations are securing their OT environments in 2025—and where others can follow.
 

Evaluate your current OT environment

The first step in building a hybrid OT security stack is to gain a comprehensive understanding of your existing environment. This includes identifying all devices, systems and applications within your OT network, including their age, function and criticality. Then, map the network topology, including connections between different segments, communication protocols and external access points.

This evaluation process must also account for how digital transformation has expanded the attack surface. The surge in IP-connected devices, remote access capabilities and cloud integrations means that traditional visibility strategies may no longer be sufficient.

Effective risk assessments now require real-time network monitoring, a clear inventory of unmanaged assets and an understanding of how legacy systems interact with modern infrastructure. Without a current and accurate understanding of the OT environment, organizations risk applying generic controls to high-consequence systems, leaving critical gaps in protection.

Develop a long-term, consequence-based approach

One of the most notable shifts in 2025 is the centralization of OT cybersecurity as a core business function, rather than a bolt-on to IT or compliance.  As a result, industries are moving beyond checklist-driven audits and adopting risk-based assessments that reflect the operational realities of modern industrial environments.
 
Consequence-based risk assessments are at the heart of this evolution. By evaluating the potential operational, safety and financial impacts of a breach, organizations can prioritize critical assets and implement security measures that are proportionate to the risks they face.
 
This shift ensures that mitigation efforts are focused where they matter most—before issues escalate. In this model, success depends not only on having the right mix of processes, procedures and tools, but also on ensuring that personnel across the organization are equipped and empowered to use them effectively.
 

Leverage existing infrastructure to accelerate security gains

In many industrial environments, the challenge isn’t a lack of tools—it’s underutilized infrastructure. Organizations can maximize the value of the security investments they’ve already made, applying them with greater precision and context to OT environments.

This was the approach taken by a major oil and gas operator managing more than 75 facilities across the U.S. Rather than overhaul its entire architecture, the company built a hybrid OT security stack that could adapt across varied sites, legacy systems and new digital infrastructure. The focus was on optimizing what was already in place, strengthening configuration and filling strategic gaps.

The implementation included tightened network segmentation using VLANs, refined firewall policies and site-to-site VPNs to isolate critical systems and reduce lateral movement. Access control was centralized through Microsoft Active Directory and a demilitarized zone (DMZ), providing better oversight of permissions and identity management. High-enforcement application allow-listing was deployed to monitor software usage and prevent unauthorized execution, and remote access was secured using multi-factor authentication and policy-based controls. Visibility was enhanced across all environments with centralized logging and dashboards, giving both IT and OT teams real-time insights into infrastructure and emerging threats.

By reconfiguring and layering existing tools in a way that reflected each facility’s operational context, the company established a consistent, risk-informed security foundation—without needing to rip and replace. This approach not only improved protection but also delivered higher uptime, stronger incident response and a more resilient OT security posture at scale.

Unify through shared environmental context

The most powerful enabler of security is the ability to share environmental context. This means translating what makes OT environments unique: how systems behave under normal conditions, what abnormal looks like, and what operational impact a security event could have in real time. It also means giving IT teams insight into the constraints OT teams face—like limited downtime windows, real-time process control requirements and legacy system limitations.

When IT and OT teams share this context, they can apply the same tools—firewalls, SIEMs, access controls—with precision. It’s no longer about whose domain a system falls under, but what the consequences are of that system being compromised and how best to defend it.

This collaboration requires governance: clearly defined roles, consistent protocols and an organizational commitment to educating personnel across disciplines. Context is what empowers those teams to move forward with confidence, under pressure.

Final thoughts

As the OT threat landscape continues to evolve, the mandate for cybersecurity teams is clear: move beyond reactive controls and siloed responsibilities toward a unified, consequence-driven approach. That starts with using the tools you already have—intentionally, contextually and collaboratively.
 
By aligning around shared outcomes, continuously reassessing risk and embedding security into daily operations, organizations can move faster than the threats they face. OT cybersecurity in 2025 isn’t about bridging a divide—it’s about building forward, together.